Tectonic Hazards
1. Earthquake hazards and their impacts
a) hazards include ground shaking, soil liquefaction, landslides and tsunamis
b) impacts include destroying ecosystems, properties and infrastructure; disrupting services; and causing injury and loss of life
2. Volcanic eruption hazards and their impacts
a) hazards include tephra, volcanic gases, lava flows, pyroclastic flows, lahars and volcanic landslides
b) impacts include destroying ecosystems, properties and infrastructure; disrupting services; and threaten public health and cause injury and loss of life
3. Benefits of volcanic eruptions and living near volcanoes
a) volcanic eruption provides fertile soil for farming after volcanic materials are broken down and weathered, and makes available valuable minerals and building materials
b) living near volcanoes allow harnessing of geothermal energy and tourism activities
Hazards associated with earthquakes.
Ground shaking
● Ruptures oil and chemical factories, polluting land and water.
● Fractures and uproot trees, causing widespread tree injury and death and damaging wildlife habitats.
● Weakens buildings, bridges, roads and railways, causing them to collapse, making it difficult to rescue people or supply emergency aid.
● Snaps water and gas pipes, resulting in water shortages and gas supply disruptions.
● Electricity and communication cables break, affecting important communication services such as tsunami warnings and television broadcasts.
● People may get trapped under collapsed buildings and infrastructure, resulting in loss of lives and injuries.
● 2010 Haiti earthquake (Mw7.0):
○ Surrounding areas around factories were polluted by oil and chemicals.
○ Debris polluted rivers.
○ More than 250,000 houses collapsed due to violent vibrations.
○ About 220,000 people were killed.
○ Water pipes ruptured, causing water shortages.
● 2010 Christchurch, New Zealand earthquakes:
Many trees were damaged and more than 300 had to be removed, reducing availability of habitats for terrestrial species.
Liquefaction
● Trees on liquefied soil sink in and tip over, damaging wildlife habitats, causing forest and biodiversity loss.
● Liquefied soil may enter rivers and smother aquatic plants, killing them.
● Sewage pipes may be broken and untreated water materials may pollute rivers, killing aquatic species.
● Buildings and other infrastructure can sink in and tip over, and the damage makes it difficult to rescue people or supply emergency aid.
● Electricity and communication cables, and water and gas pipes can sink in and snap, disrupting supply of these services.
● Roads and railways above liquefied soil can sink in and get damaged, making it difficult to rescue people or supply emergency aid.
● People may get trapped under collapsed buildings and infrastructure, resulting in loss of lives and injuries.
● 2010-2011 Christchurch, New Zealand earthquakes:
○ Triggered severe liquefaction, as the city lies on a former swamp area where soils are loose and saturated.
○ More than 60,000 residential buildings and infrastructure covering about one-third of the city area were damaged.
○ Liquefied soil entered rivers and untreated sewage from broken pipes polluted rivers. This resulted in the reduction of some species such as the caddisflies.
Landslides
● Fast-moving debris can bury huge areas of forest and wetlands.
● Rivers can be polluted with debris, killing aquatic life.
● Rivers can be blocked, causing floods that can damage nearby ecosystems and properties.
● Debris can bury villages and farms, destroying properties and infrastructure.
● Debris can snap electricity and communication cables, and water and gas pipes, disrupting supply of these services.
● Roads and railways can be blocked by debris, making it difficult to rescue people or supply emergency aid.
● Debris can bury people or hit them, causing injuries and loss of lives.
● Debris can block rivers, resulting in floods, which can drown people.
● 2018 Papua New Guinea earthquake (Mw7.5):
○ Flooding due to landslides that caused huge amounts of debris to enter the rivers.
○ Destroyed forests.
○ Polluted waters and killed fish.
● 2008 Great Sichuan, China Earthquake:
○ Triggered more than 15,000 landslides.
○ Destroyed many buildings and infrastructure.
○ Caused nearly 20,000 deaths.
Tsunamis
● Tsunamis are a series of ocean waves which can be caused by undersea earthquakes.
● Tsunamis can travel over thousands of kilometres and devastate huge areas of coastline.
● Tsunamis may be formed by:
○ The movement of the sea floor during a large earthquake at subduction zones;
○ An explosive underwater volcanic eruption;
○ An underwater landslide; and
○ A landslide above sea level which causes materials to plunge into the water
● The seawater can flood huge areas of coastal wetlands and forests, damaging habitats.
● Large amounts of debris carried in by the waves can pollute these areas, damaging ecosystems and killing wildlife.
● Fast moving waters and the large amounts of debris carried in by the waves can sweep away buildings and infrastructure, destroying them.
● Fast moving waters and the large amount of debris carried in by the waves can snap electricity and communication cables, disrupting supply of these services.
● Fast moving water can sweep away roads and railways, making it difficult to rescue people or supply emergency aid.
● Sweeping waters can drown people.
● Large amounts of debris carried in by the waves can hit and kill people.
● 2004 Indian Ocean Tsunami:
○ Triggered by a 9.1 Mw undersea earthquake near Sumatra, Indonesia.
○ Tsunami waves slammed into the coasts of 11 Indian Ocean countries, from Indonesia to Somalia in Africa.
○ More than 230,000 people were killed and entire coastlines and habitats were destroyed.
● 2011 Tohoku, Japan earthquake (Mw 9.0)
○ Triggered a tsunami up to 40m in height.
○ Waves destroyed homes and infrastructure.
○ Tsunami waves carried debris inland, flooding and polluting large areas of land.
○ Coastal city of Sendai suffered extensive damage and half its population was killed.
○ In Iwate, 70,000 pine trees were knocked down, resulting in forest and biodiversity loss.
○ The tsunami hit the Pacific islands, devastating the ecosystems.
○ Entire bird nesting sites were lost, and more than 100,000 Layson Albatross Chicks were killed, and thousands of fish were washed ashore where they suffocated.
Hazards associated with Volcanic Eruptions
Tephra
● Ash can be carried thousands of kilometres by prevailing winds, polluting huge areas of forests, rivers and other habitats, and destroying ecosystems.
● Ash can suffocate and kill wildlife.
● Ash can cause blindness to birds, with their eyelids getting gummed together.
● Volcanic bombs, ranging from a few centimeters to the size of vehicles, can hit properties, damaging them.
● Ashfall can accumulate on roofs of buildings. When saturated with water, the weight of ash can double, causing building roofs to collapse.
● Being corrosive, ash weakens building structures, making them more likely to collapse.
● Thick blankets of ash can damage farmland, suffocating crops and destroying livelihoods.
● Ash particles can damage plane engines, leading to closure of airspaces, and disrupting air transportation services.
● Volcanic bombs can hit people, causing injuries and loss of lives.
● Ashfall can cause respiratory problems, eye irritation and suffocate people.
● 1991 Mount Pinatubo eruption in the Philippines:
○ Emitted huge amounts of ash.
○ Buried more than 180 km² of forests in ash of about 25 cm.
○ Destroyed 800 km² of rice fields, affecting the livelihoods of many farmers.
○ Seven airports in the Philippines had to be closed and many flights were cancelled, disrupting transport.
○ Some planes were also damaged.
Volcanic gases
● Volcanic eruptions can release large amounts of toxic gases such as sulfur dioxide and carbon dioxide.
● Sulfur dioxide results in acid rain when it reacts with water in the air, which can damage vegetation, soil and kill wildlife.
● Cold carbon dioxide is heavier than air, so it can become concentrated in low-lying volcanic areas such as river valleys.
● Large amounts of carbon dioxide in the air can kill wildlife, and in the soil, can destroy vegetation.
● Sulfur dioxide results in acid rain, which can corrode buildings and infrastructure.
● Sulfur dioxide irritates skin, eyes, nose and throat.
● Air containing over 3% carbon dioxide can cause headaches and breathing difficulties, and when it exceeds 15%, may cause death.
● Dieng volcano eruption in Indonesia in 1979: Released deadly amounts of carbon dioxide and killed about 150 people.
Lava flow
● Lava flows are extremely hot and can travel over some distance within the geographic region of the volcano.
● However, deaths caused directly by lava flows are uncommon as people can easily move out of its way.
● Hot, low-silica lava can travel over some distance, destroying forests, other habitats and ecosystems within these habitats.
● Lava can burn through homes, properties and infrastructure.
● Lava can destroy electricity and communication cables, and water and gas pipes, disrupting supply of these services. 2018 Kilauea eruption in Hawaii:
○ Far-reaching lava flows destroyed more than 600 homes.
○ Destroyed huge areas of forests and ecosystems.
○ Telephone and power lines were damaged, causing widespread communication outrages.
Pyroclastic flow
● Pyroclastic flows occur when a column of hot ash and gas gets thrown up into the air, and falls back to the ground under the pull of gravity.
● A pyroclastic flow is a hot cloud of gas, ash and rocks travelling down the slopes of a volcano at great speeds
○ Unable to survive if property or person is in its path with temperatures of up to 700℃.
○ Unable to escape given that the speed is more than 200km/h.
● Typically, pyroclastic flows can travel several kilometers.
● Huge areas of forests may be destroyed, resulting in loss of biodiversity.
● Thick layers of ash cover the path of the flows, polluting huge areas of forests.
● The hot flows can burn through all homes, properties and infrastructure in its path.
● The hot flows can destroy electricity and communication cables, and gas pipes, disrupting supply of these services.
● The extreme temperatures can burn, and kill people in a fraction of a second.
● 2010 Merapi eruption in Indonesia:
○ Blasted a series of pyroclastic flows down the slopes of the volcano which were inhabited by many villagers.
○ About 350 people were killed, mostly due to burns and blast injuries.
○ Huge areas of forest were burnt.
Lahar
● Lahars are mudflows comprising water and volcanic ash. Lahars are formed when huge amounts of ash and rocks ejected during an eruption mix with water.
● Lahars can occur when:
● Pyroclastic flows melt snow and ice, and mix with the water on the volcanic cone as they travel down.
● Intense rainfall washes down the ash.
● Lahars are capable of flowing at high speeds (up to 200km/h), and over considerable distances within the geographic region of the volcano.
● Lahars can cover forests and other ecosystems with thick mud which hardens like concrete, destroying them.
● Lahars can pollute rivers, killing aquatic life.
● Lahars can bury houses and buildings, destroying them.
● Lahars can cover farms with thick mud, which hardens like concrete, damaging them.
● Lahars can damage communication cables, and water and gas pipes, disrupting supply of these services.
● Roads and railways can be blocked by debris, making it difficult to rescue people or supply emergency aid.
● Lahars can bury houses and its residents, resulting in loss of lives.
● 1985 Nevado Del Ruiz eruption in Colombia:
○ Released huge amounts of ash and volcanic rocks which melted snow and ice.
○ The meltwater mixed with ash and rocks to form lahars.
○ Fast-moving lahars buried more than 20,000 people in the nearby town of Armero within seconds.
○ Rivers were highly muddied by the lahars, killing many fish.
Volcanic Landslides
● Volcanic landslides are common on tall and steep volcanic cones which comprise thousands of solidified lava layers and loose tephra.
● The blast from an explosive eruption can trigger the downward movement of loose volcanic material, causing a landslide.
● The high velocity and great momentum of landslides allow them to travel considerable distances within the geographic region of the volcano.
● Fast-moving debris can bury huge areas of forest and wetlands.
● Rivers can be polluted with debris, killing aquatic life.
● Rivers can be blocked, causing floods that can damage nearby ecosystems and properties.
● Debris can bury villages and farms, destroying properties and infrastructure.
● Debris can snap electricity and communication cables, and water and gas pipes, disrupting supply of these services.
● Roads and railways can be blocked by debris, making it difficult to rescue people or supply emergency aid.
● 1980 Mt St Helens eruption in USA:
○ North face of the volcanic cone collapsed.
○ Caused volcanic landslides that traveled as far as 23km from the volcano.
○ Destroyed huge areas of land and killed many wildlife
The Destruction of the Colombian City of Armero During the 1985 Volcanic Eruption of the Nevado del Ruiz.
In March 2011, Japan experienced a magnitude 9.0 earthquake, the strongest earthquake recorded in its history. This earthquake triggered a tsunami which affected many coastal areas of Japan, especially the Tohoku region. Approximately 20,000 people lost their lives and there was widespread infrastructural damage all over Japan. Watch the video below to learn more about this earthquake and tsunami.
On 28th September 2018, Palu, Indonesia, was hit by a high magnitude 7.5 earthquake. The earthquake caused major soil liquefaction in areas in and around Palu. In two locations this led to mudflows in which many buildings became submerged causing hundreds of deaths with many more missing.
A 7.5 Earthquake struck the Indonesian island of Sulawesi followed by a tsunami on 28 Sept 2018.
What are the factors which led to the city of Palu experiencing the greatest damage and loss of lives?
Where are the areas affected?
Why do Indonesia experience frequent earthquakes?
What have been done to mitigate the impacts of earthquake?
Who are the ones affected by the earthquake?
How does the people respond to the earthquake to mitigate the impacts of earthquake?
How was the tsunamis formed? (this tsunamis which hit Palu was unique as it was not an offshore earthquake)
Strong aftershocks have continued to hit Sulawesi, where the major quake and tsunami killed at least 408 people and injured 500.
https://www.channelnewsasia.com/news/asia/indonesia-palu-earthquake-tsunami-dead-rescuers-10770998
The Turkey-Syria Earthquake on 6 Feb 2023 has resulted in total death toll of more than 46,000 (as at 20 Feb 2023)
When did the main earthquake occur?
Where is the epicenter of the earthquake?
What are the factors which affect the extent of damage?
How effective are the short term responses?
The Arabian plate moving northwards and slide past the Anatolian plate. This resulted in the building of stress and the release of the stress lead to the land slipping and faulting occurs.
Factors contributing to the extent of damage
1. The epicentre was about 26 km east of the Turkish city of Nurdagi.
2. The intensity of the earthquake was high at a magnitude of 7.8, amplified by the shallow depth of 18km, which caused many buildings to collapse.
3. The time of occurrence as the incident occurred in the early hours of the morning at 4.17am, when people were inside the buildings and sleeping.
4. The sturdiness of the buildings as many of the infrastructure are not resistant to earthquake in South Turkey and especially Syria. There were weak enforcement of building codes and many violations including homes built without permits, buildings that added extra floors or expanded balconies without authorisation, and the existence of squatter inhabited by low-income families.
5. There had not been a major earthquake for more than 200 years or any warning signs, so the level of preparedness would be less compared to a region which is more used to dealing with tremors.
A 6.8 magnitude earthquake that struck the High Atlas Mountains late on Sep 8 2023 killed 2,946 people and injured 5,674, making it Morocco's deadliest since 1960 and most powerful since1900.
Why do you think the earthquake is so hazardus at Morocco?
Earthquake magnitude 7.4 in Taiwan April 2024
https://olevelgeog.blogspot.com/2024/04/magnitude-72-earthquake-hit-taiwan.html
Volcanic island eruption on White Island, New Zealand, 9 Dec 2019 has proven fatal, killing 19 with 2 still missing and several hospitalised with severe burns.
The volcano attracts as many as 10,000 tourists every year.
What are the risks involved in visiting a volcano?
Why do you think many tourists visit the volcano despite the risks?
Interesting virtual exploration of the volcano unfolding the disaster.
Iceland experienced three eruptions since Dec 2023.
When did the volcano erupt?
Why is Iceland prone to volcanic eruption?
What type of volcanoes are found in Iceland?
How did the volcanic eruption affect the people?
